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Re: Failing Malloc

From James Kuyper <jameskuyper@verizon.net>
Newsgroups comp.lang.c
Subject Re: Failing Malloc
Date 2012-09-12 17:37 -0400
Organization A noiseless patient Spider
Message-ID <50510086.9010908@verizon.net> (permalink)
References <k2qq2i$aba$1@speranza.aioe.org> <L864s.41309$Ax.33657@fx18.am4> <k2qrlc$ea5$1@speranza.aioe.org>

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On 09/12/2012 04:34 PM, Eric wrote:
...
> Sorry maybe I wasn't too clear. I would like to get the Malloc call to 
> succeed if I redo it. Or get some alternative memory eg from the stack or 
> swop.

When it is possible to do something like that (which is seldom the
case), it is essential that you have one or more blocks of memory
somewhere that you can free(), so that you can retry the malloc() with
some chance of having it succeed.
Problem: if you allocated those other blocks of memory, you either need
to write to them, or you need access to information that has already
been written to them. If neither of those are the case, those other
blocks should either a) not have been allocated yet or b) should have
already been free()d.
Therefore, you're going to have to figure out some alternative way of
dealing with whatever it is that you allocated those other memory blocks
for, an alternative that does not require as much memory. That's the
hard part, and is one reason why this approach is seldom used.

An example that could come up in my own code (if it were radically
re-designed). Several of my programs process one scan of data (13,540
pixels) at a time. Those programs could, instead, have been written to
process only one frame of data (10 pixels) at a time. There's some
inefficiency to doing so, so it would run a bit slower, but it would
also require a lot less memory.

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Thread

Failing Malloc Eric <nospam@nospam.com> - 2012-09-12 20:07 +0000
  Re: Failing Malloc Xavier Roche <xroche@free.fr.NOSPAM.invalid> - 2012-09-12 22:12 +0200
    Re: Failing Malloc William Ahern <william@wilbur.25thandClement.com> - 2012-09-12 14:25 -0700
  Re: Failing Malloc Andrew Cooper <andrew@nospam.example.com> - 2012-09-12 21:21 +0100
    Re: Failing Malloc Eric <nospam@nospam.com> - 2012-09-12 20:34 +0000
      Re: Failing Malloc Paul N <gw7rib@aol.com> - 2012-09-12 13:46 -0700
        Re: Failing Malloc Eric <nospam@nospam.com> - 2012-09-13 20:21 +0000
          Re: Failing Malloc Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-09-13 17:31 -0400
          Re: Failing Malloc James Kuyper <jameskuyper@verizon.net> - 2012-09-13 17:57 -0400
      Re: Failing Malloc John Gordon <gordon@panix.com> - 2012-09-12 20:55 +0000
        Re: Failing Malloc William Ahern <william@wilbur.25thandClement.com> - 2012-09-12 14:33 -0700
        Re: Failing Malloc falk@rahul.net (Edward A. Falk) - 2012-09-13 22:43 +0000
      Re: Failing Malloc James Kuyper <jameskuyper@verizon.net> - 2012-09-12 17:37 -0400
      Re: Failing Malloc Johann Klammer <klammerj@NOSPAM.a1.net> - 2012-09-13 08:57 +0200
  Re: Failing Malloc James Kuyper <jameskuyper@verizon.net> - 2012-09-12 17:20 -0400
    Re: Failing Malloc Ian Collins <ian-news@hotmail.com> - 2012-09-13 09:27 +1200
      Re: Failing Malloc James Kuyper <jameskuyper@verizon.net> - 2012-09-12 17:56 -0400
        Re: Failing Malloc Ian Collins <ian-news@hotmail.com> - 2012-09-13 10:28 +1200
          Re: Failing Malloc James Kuyper <jameskuyper@verizon.net> - 2012-09-12 18:57 -0400
            Re: Failing Malloc William Ahern <william@wilbur.25thandClement.com> - 2012-09-12 16:21 -0700
            Re: Failing Malloc Ian Collins <ian-news@hotmail.com> - 2012-09-13 12:07 +1200
              Re: Failing Malloc James Kuyper <jameskuyper@verizon.net> - 2012-09-13 13:18 -0400
                Re: Failing Malloc Ian Collins <ian-news@hotmail.com> - 2012-09-14 07:37 +1200
                Re: Failing Malloc James Kuyper <jameskuyper@verizon.net> - 2012-09-13 16:05 -0400
                Re: Failing Malloc William Ahern <william@wilbur.25thandClement.com> - 2012-09-13 14:21 -0700
                Re: Failing Malloc James Kuyper <jameskuyper@verizon.net> - 2012-09-13 17:38 -0400
                Re: Failing Malloc William Ahern <william@wilbur.25thandClement.com> - 2012-09-13 14:03 -0700
                Re: Failing Malloc Ian Collins <ian-news@hotmail.com> - 2012-09-15 10:01 +1200
            Re: Failing Malloc Philip Lantz <prl@canterey.us> - 2012-09-14 02:50 -0700
  Re: Failing Malloc Kaz Kylheku <kaz@kylheku.com> - 2012-09-12 21:36 +0000
  Re: Failing Malloc Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-09-12 17:41 -0400
  Re: Failing Malloc Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2012-09-12 16:07 -0600
    Re: Failing Malloc "christian.bau" <christian.bau@cbau.wanadoo.co.uk> - 2012-09-12 16:03 -0700
  Re: Failing Malloc Kenneth Brody <kenbrody@spamcop.net> - 2012-09-12 19:24 -0400
  Re: Failing Malloc The Great Firewall of China Blue <chine.bleu@yahoo.com> - 2012-09-12 16:34 -0700
  Re: Failing Malloc Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-09-13 00:14 -0700

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